The present invention relates to tubing for use in and an intravenous flow controller and more specifically to a novel internal cross-sectional shape of such tubing and a novel flow controller for taking advantage of the novel internal cross-sectional shape of the tubing as well as additional novel features.
Controllers for controlling the drop or flow rate through an intravenous tube are well known in the art and are exemplified by devices illustrated in U.S. Pat. Nos. 3,991,972, 4,137,940 and 4,300,552. The forces required of such devices to completely block flow through the standard round I.V. tube are typically as much as three pounds. Only a relatively small amount of the force is required to close the main body of the tube, the majority of the force being required to close small circular openings at the outer edges of the compressed tube, a phenomenon commonly known as the dog-bone effect. The high pressure required to close round tubing will deform the tube wall. Upon release of the pressure, during initial fluid flow, the deformation in the tube wall requires time to return to its original thickness. This element of time undesirably affects the response time of the control device. In addition, due to the high forces required to fully close the round tubing, when pressure is released the tubing will have a tendency to stick together.